We present a new model for the formation of dense clumps and pillars
around H II regions based on shocks curvature at the interface
between a H II region and a molecular cloud. UV radiation
leads to the formation of an ionization front and of a shock
ahead. The gas is compressed between them forming a dense shell at the
interface. This shell may be curved due to initial interface or
density modulation caused by the turbulence of the molecular
cloud. Low curvature leads to instabilities in the shell that form
dense clumps while sufficiently curved shells collapse on itself to
form pillars. When turbulence is high compared to the ionized-gas
pressure, bubbles of cold gas have sufficient kinetic energy to
penetrate into the H II region and detach themselves from the
parent cloud, forming cometary globules.
Using computational simulations, we show that these new models are
extremely efficient to form dense clumps and stable and growing
elongated structures, pillars, in which star formation might
occur. The inclusion of turbulence in the model shows its importance
in the formation of cometary globules. The code used for the
simulation is the HERACLES code, that comprises hydrodynamics with
various equation of state, radiative transfer, gravity, cooling and
heating. We also present observational diagnostic of these new models
based on the line-of-sight velocity profiles and probability density
functions.